Research on the Method of Measurement of Nonlinear Refractive Index of Optical Materials by Interference of Capillary

With the intensity distribution of interference fringes formed by a capillary filled with transparency liquid, the variations in refractive index (RI) of nonlinear optical materials, corresponding to change of the intensity at the centre of fringes for a period, are deduced. Using this conclusion, we measure variations in RI of water solution of methyl orange (MO) excited by laser at 441.6nm. As an experimental result, the change of RI is 0.00216 and the corresponding effective index of refraction is -1.65×10-10 m2W-1. So, it can be used to measure nonlinear optical materials as a novel and simple method.